Bicycle crank arm

摘要

A hollow bicycle crank arm has a central tubular portion to reduce weight and two mounting-boss portions for mounting a crank spindle and pedal during use. A crank arm base is forged or cast with a relatively thin back and sides, preferably out of aluminum or magnesium. The crank arm base has a generally C-shaped cross section. An arm cover has a top and sides and is made from stamped steel or titanium. The cover is placed over the open crank arm base to enclose a significant hollow section. The stamped arm cover does not require any threading or welding. It can be made using a very inexpensive stamping process. The crank arm can be made using relatively inexpensive traditional manufacturing processes such as die casting or forging.